Image pick-up module transmission arrangement for a scanner

ABSTRACT

An image pick-up module transmission arrangement includes a top cover holding a transparent glass above a scanning path defined therein and two racks along two opposite sides of the scanning path, two guide rails bilaterally fixedly fastened to the top cover at a bottom side of the scanning path, an image pick-up module reciprocated in the scanning path along the guide rails, the image pick-up module having pulleys revolvably supported on the guide rails and spring leaves disposed in contact with the guide rails, and a transmission shaft mounted in the image pick-up module, the transmission shaft having two gear wheels at two opposite ends meshed with the racks, the gear wheels being rotated clockwise/counter-clockwise by a power drive in the image pick-up module, causing the image pick-up module to be reciprocated in the scanning path along the guide rails.

BACKGROUND OF THE INVENTION

The present invention relates to a scanner, and more specifically to animage pick-up module transmission arrangement for a scanner whichenables the image pick-up module to be stably smoothly reciprocated inthe scanning path to positively pick up the image of document up.

Scanners have been intensively used with computers in offices for textand graphic document data input. A regular scanner for this purpose isgenerally comprised of a transparent glass, an image pick-up module, atransmission mechanism, an electronic control circuit, a power supplyunit, and a machine base. During the operation of a scanner, the lightpath must be maintained stable so that the image of document can bepositively picked up by the image pick-up module. If the light path isnot maintained stable, image distortion becomes inevitable. To a highresolution scanner of CIS (contact image sensor) type scanner, therequirement for a stable light path is critical.

FIG. 1 shows an image pick-up module transmission arrangement for ascanner according to the prior art. According to this arrangement, theimage pick-up module is driven to move back and forth in the scanningpath by a motor drive through a belt transmission mechanism. Because thebelt transmission mechanism produces vibration when the motor drive isstarted, the reciprocating motion of the image pick-up module which isunstable may affect the scanning quality. Furthermore, because the belttransmission mechanism is mounted in the machine base, the outer shellof the scanner tends to be put out of shape due to change of ambienttemperature and humility. When the outer shell of the scanner isdeformed, the light path becomes unstable, in consequence the scanningquality is affected.

SUMMARY OF THE INVENTION

The present invention has been accomplished to provide an image pick-uptransmission module which eliminates the aforesaid problems. Accordingto the present invention, the top cover of the scanner holds atransparent glass above the scanning path and two racks along twoopposite sides of the scanning path, the image pick-up module issupported on two guide rails, which are bilaterally fixedly fastened tothe top cover at the bottom of the scanning path, and a transmissionshaft is revolvably mounted in the image pick-up module, and coupled tothe racks by gear wheels. The gear wheels are rotatedclockwise/counter-clockwise by a power drive in the image pick-upmodule, causing the image pick-up module to be reciprocated in thescanning path along the guide rails. Because the top cover of thescanner is stretched by the transparent glass, ambient temperature andhumility changes do not deform the top cover easily. Furthermore,because the image pick-up module is reciprocated in the scanning path bymeans of rotating the gear wheels along the racks, the reciprocatingmotion of the image pick-up module is stable, and little noise orvibration is produced during the reciprocating motion of the imagepick-up module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an image pick-up moduletransmission arrangement for a scanner according to the prior art.

FIG. 2 is a perspective view of the present invention.

FIG. 3 is a side view in section of the present invention.

FIG. 4 is an enlarged view of a part of the present invention, showingthe spring leaf supported on the guide rail.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 2, the present invention comprises generally at leastone for example two guide rails 20, an image pick-up module 21, atransmission shaft 23, a transparent glass 201, and a top cover 22.

The transparent glass 201 is a flat glass plate integral with the topcover 22. The top cover 22 comprises two racks 202 arranged in parallelalong two opposite lateral sides of the scanning path. The guide rails20 are arranged in parallel along the two lateral sides of the scanningpath below the racks 202. The image pick-up module 21 comprises anoptical scanning system and a power drive. The transmission shaft 23 ismounted in the image pick-up module 21, having two opposite endsrespectively extended out of two opposite lateral sides of the imagepick-up module 21. Two driven gear wheels 203 are respectively mountedon the ends of the transmission shaft 23 outside the image pick-upmodule 21. The driven gear wheels 203 are respectively meshed with theracks 202, and rotated by the power drive in the image pick-up module21. When the driven gear wheels 203 are rotated, the image pick-upmodule 21 is forced to move between the racks 202 and the guide rails 20along the scanning path. Because the driven gear wheels 203 are fixedlymounted on the two opposite ends of the transmission shaft 23, they aresynchronously rotated or stopped. As an alternate form of the presentinvention friction wheels may be used instead of the driven gear wheels203. In this case, tracks are used instead of the racks 202 to matchwith the friction wheels. The guide rails 20 bear the image pick-upmodule 21 and guide its reciprocating motion. Two pulleys 204 arerespectively provided at the two opposite lateral sides of the imagepick-up module 21, and revolvably supported on the guide rails 20,enabling the image pick-up module 21 to be smoothly stably moved alongthe guide rails 20 (In the drawings, only one pulley 204 is shown). Twoholder frames 205 are fixedly transversely fastened to the top cover 22at two opposite ends of the scanning path to hold the guide rails 20 inplace (in FIG. 3, only one holder frame 205 is shown), enabling thedistance between the guide rails 20 and the transparent glass 201 of thetop cover 22 to be maintained and unchanged. Because the cover panel ofthe top cover is formed of the transparent glass 201, the structuralstrength of the top cover 22 is sufficient to support the wholetransmission mechanism, and the top cover 22 does not deform easily dueto a change of ambient temperature.

In order to eliminate vibration and noise between the driven gear wheels203 and the racks 202 during the operation of the scanner, spring leaves200 are provided at the bottom side wall of the image pick-up module 21and respectively disposed in contact with the guide rails 20 at the top(in the drawings, only one spring leaf 200 is shown).

While only one embodiment of the present invention has been shown anddescribed, it will be understood that various modifications and changescould be made thereunto without departing from the spirit and scope ofthe invention disclosed.

What the invention claimed is:
 1. An image pick-up module transmissionarrangement comprising: a top cover defining a scanning path, said topcover including two racks longitudinally arranged in parallelrespectively along two opposing lateral sides of said scanning path; atransparent glass plate integral with said top cover above said scanningpath; at least one guide rail fixedly fastened to said top cover andspaced therefrom, said at least one guide rail extending longitudinallyand parallel to said scanning path; an image pick-up module displaceablysupported on said at least one guide rail and reciprocated along saidscanning path on said at least one guide rail, said image pick-up moduleincluding (a) at least one pulley pivotally coupled thereto and rollablymounted on said at least one guide rail, and (b) at least one springleaf longitudinally displaced from said at least one pulley and mountedto a lower surface of said image pick-up module, said spring leaf havinga distal end portion disposed in sliding contact with said at least oneguide rail, said image pick-up module having an optical scanning systemand a power drive mounted therein; and a transmission shaft mounted insaid image pick-up module, said transmission shaft having two oppositeends respectively extending out from two opposite lateral sides of saidimage pick-up module, said transmission shaft having two driven gearwheels respectively fixedly mounted on two opposite ends thereof andrespectively meshingly engaged with said two racks, said driven gearwheels being rotated clockwise/counter-clockwise by said power drive ofsaid image pick-up module for causing said image pick-up module to bereciprocated along said scanning path.
 2. An image pick-up moduletransmission arrangement comprising: a top cover defining a scanningpath, said top cover including two tracks longitudinally arranged inparallel respectively along two opposing lateral sides of said scanningpath; a transparent glass plate integral with said top cover above saidscanning path; at least one guide rail fixedly fastened to said topcover and spaced therefrom, said at least one guide rail extendinglongitudinally and parallel to said scanning path; an image pick-upmodule displaceably supported on said at least one guide rail andreciprocated along said scanning path on said at least one guide rail,said image pick-up module including (a) at least one pulley pivotallycoupled thereto and rollably mounted on said at least one guide rail,and (b) at least one spring leaf longitudinally displaced from said atleast one pulley and mounted to a lower surface of said image pick-upmodule, said spring leaf having a distal end portion disposed in slidingcontact with said at least one guide rail, said image pick-up modulehaving an optical scanning system and a power drive mounted therein; anda transmission shaft mounted in said image pick-up module, saidtransmission shaft having two opposite ends respectively extending outfrom two opposite lateral sides of said image pick-up module, saidtransmission shaft having two friction wheels respectively fixedlymounted on two opposite ends thereof and respectively disposed incontact with said two tracks, said friction wheels being rotatedclockwise/counter-clockwise by said power drive of said image pick-upmodule for causing said image pick-up module to be reciprocated alongsaid scanning path.